High heat flux experiments of plasma facing components for next fusion devices

To develop plasma facing components (PFC) for the next fusion devices, JAERI has been carrying out high heat flux and high particle flux experiments on the divertor modules and candidate materials in JAERI Electron Beam Irradiation System (JEBIS). (1) To investigate the feasibility and the advantage of a saddle type divertor modules, which has unidirectional (1-D) carbon fiber reinforced carbon composites (CFCs) armour tile brazed on OFHC-copper heat sink, high heat flux experiments have been carried out under a cyclic heat load of 24.5 MW/m ² at a duration of 30 s. After 1000 cycles, no degradation of thermal response and no defect in the module was found. (2) To reduce the residual stress around the brazed interface, we have developed small specimens with the new materials combination of W-30Cu composites heat sink and 1-D CFC armour tile and carried out the high heat flux experiments under a cyclic heat load of 15 MW/m² at a duration of 20 s. After 1,000 cycles, no cracks have been observed at the interface. (3) To evaluate the erosion of armour tiles by high heat flux, we have measured the erosion of CFCs and isotropic graphite up to 1100°C under a heat flux of 1800 MW/m² for the duration of 1.5~2 ms. It is clear that the erosion of carbon based materials increases with the bulk temperature and decreases with the thermal conductivity. (4) To evaluate the erosion by high particle flux, we have developed a new irradiation device, which have a high hydrogen particle flux of 10²¹/m²/s at 50~100 eV